This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
The major components and processes associated with the presence of subsurface hydrocarbon accumulations in a sedimentary basin include (1) the presence of a source rock from which hydrocarbons can be generated, (2) the burial of the source rock to sufficient temperatures and pressures to result in the generation and expulsion of liquid hydrocarbons from a source rock (source maturity), (3) presence of a reservoir of sufficient adequacy to store hydrocarbons, (4) migration of liquid hydrocarbons to and accumulation in a reservoir, and (5) a trap and a seal that prevents significant leakage of hydrocarbons from the reservoir. The relative timing of each of these components and processes are utilized to determine the existence of any accumulation. Each of these components should be present for a subsurface hydrocarbon accumulation to exist.
The presence of some of these components can be addressed adequately using conventional techniques including by direct observation. For example, the presence of hydrocarbons at a seep location or in subsurface sediments suggests the presence of a source rock that has reached sufficient depths to generate hydrocarbons and that these hydrocarbons have been expulsed from the source. Similarly, during drilling of a well reservoir lithologies may be encountered that confirm the presence of a reservoir. Though helping to confirm presence, such evidence alone typically provides insufficient information to develop exploration, production, and development strategies. For example, if multiple source rocks are present in the subsurface, the presence of hydrocarbons at a seep or in the subsurface may not provide the information necessary to determine which source rock has generated the hydrocarbons.
In addition to direct observations techniques, modeling, such as basin modeling, can be used to provide estimates on some of these components. For example, basin modeling can be used to predict the time in the past that source rocks reached sufficient temperatures to generate hydrocarbons, and can further be used to predict how much and what type of hydrocarbons (e.g., oil and/or gas) were generated through some knowledge of the depths and temperatures the source rock reached as well as characteristics of the source rock. This information can be provided by direct temperature information (e.g., fluid inclusions present with source intervals that may or may not have been uplifted can be used to provide a minimum temperature that a source rock has experienced). Alternatively, the composition of hydrocarbons sampled in the subsurface or at the surface can be used to determine what maturities source rocks have reached when the hydrocarbons have a common origin from one source interval. Those maturities are a function of the time and temperature of burial, and therefore provide an indirect estimate of temperature history. However, significant uncertainty results when direct temperature information from the source rock is not available or when sampled hydrocarbons represent mixtures of hydrocarbons that were produced from different source intervals within the subsurface. Given this uncertainty, it can often be difficult to determine the timing of source rock maturation and migration of hydrocarbons. In addition, it is often difficult to determine, in any systems where multiple source rocks are potentially present, which source rock is responsible for the generation of hydrocarbons that may ultimately migrate to an accumulation. Addressing such questions may de-risk the components of a hydrocarbon system. Such information can then be used to explore for hydrocarbons both on a local and regional basis.
As such, there is a need for enhanced techniques that may effectively determine the presence of source rocks within a hydrocarbon system and that can place constraints on the timing of hydrocarbon generation from these sources. In particular, an efficient and cost effective method for determining the maturity or temperatures that source rock(s) have experienced during burial and the time at which source rock(s) reach maturities (e.g., temperatures and pressures) sufficient to generate hydrocarbons, may provide a valuable tool that could be used in hydrocarbon exploration at various business stages, from frontier exploration to extension of proven plays or high-grading prospects in proven plays through field development and exploitation.